Hi Eric, I have understood from the document, that for each file, we have 3 extra blocks (indirect) that refer to : - the group descriptor - the block bitmap - the inode bitmap Is that right? If not, to what the indirect blocks refer to? and are there always only 3 blocks for each file in ext2/3fs? Best regards youness <div class="gmail_quote">On Tue, Aug 18, 2009 at 4:45 PM, Eric Sandeen <<a href="mailto:sandeen@redhat.com">sandeen@redhat.com</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div><div></div><div class="h5">Youness HAFFANE wrote: > > Hi, > > I'm trying to understand why extra blocks are added when you create a > file in the ext3 fs: > > for example, let's create a file of 1111 blocks (4096 bytes for each block) > > $ dd if=/dev/zero of=foo bs=4096 count=1111 > > the real occupation disk is then: > > $ du -B 4096 foo > 1114 > > instead of 1111 > > So where the 3 extra blocks come from? </div></div>from the indirect blocks. This is how ext2/3 keep track of the layout of the file. see <a href="http://e2fsprogs.sourceforge.net/ext2intro.html" target="_blank">http://e2fsprogs.sourceforge.net/ext2intro.html</a> and in particular the diagram: <a href="http://e2fsprogs.sourceforge.net/ext2-inode.gif" target="_blank">http://e2fsprogs.sourceforge.net/ext2-inode.gif</a> in that paper. -Eric > Thanks for help! > > youness > > -- </blockquote></div> -- Y.